The real issue with these stupid web tricks is not really how much Javascript is involved, it's one of usability . . . see webpagesthatsuck.com. People aren't impressed by cool widgets, but the site owners sure are. :-)
How much are they losing? If they code it right . . . none.
The way most Javascript stuff is
supposed to work - even Jquery - is via progressive enhancement (or graceful degradation, take your pick. :-) ) When you see this
<a href="real-url.html" onclick="return some_javascript();">Blah</a>
(or it's equivalent externally assigned) They lose nothing. But this,
<a href="#" onclick="return some_javascript();">Blah</a>
or
<a href="javascript:some_javascript();">Blah</a>
A lot. It renders the content inaccessible so definitely, losing a lot. But I guess the redeeming factor is, the developers/site owners don't care. They justify their decision with the same old arguments - most of the world has Javascript enabled, I don't care about non-Javascript users, either get up to speed or get out. Apple can get away with hostile marketing, most of us can't, and shouldn't.
I talk to so many people every day - ordinary people - housewives, grandparents, users who couldn't care less about bells and whistles, they just trust in what their perceived authorities tell them - who, for one reason or another, have Javascript and Flash off because someone told them it's how you get hacked. Or they run AVG software that disables most Javascript and trust it openly. There is a huge market out there for accessible sites, Javascript or not, I refuse to turn them away because my ego says so.
What gets me about all this is that it's so EASY to make your Javascript accessible. It really is.
